This invention relates to a process for forming a circuit board. More particularly, this invention relates to a method for applying electrically conducting paths to a support of an insulating material.
The support can be designed as a flat plate or as a body with planes at different heights or with planes at an angle to one another. Supports with conductive paths for electrical current are primarily used in electrical and electronic miniature devices.
From the German Utility Model No. 1 966 250, an electronic circuit board arrangement is known in which metal layers are applied as current paths on a support consisting of an insulating material. The support is a three-dimensional body consisting of a well known plastic, such as of ABS polymers. In particular an ABS graft polymerizate is disclosed onto which the current paths are applied electrolytically.
A method of forming conductive paths is known from the following article: Rempel, reprint "New Observations on the Chemogalvanic Metallization of Form Bodies of ABS Polymerizates" from "Fachberichte fur Oberflachentechnik" (Technical Reports on Surface Technology) 1970. This method involved the following steps: attacking the butadiene component by etching, especially with chromic sulfuric acid; coating it with lacquer in the desired pattern; precipitating a very thick metal layer autocatalytically; and then applying thereon electrolytically the metal layer which forms the current path.
The method in Rempel is associated with a number of difficulties and creates environmental hazards because of the use of chromic sulfuric acid in etching. Further, in production, it was generally not possible to produce three-dimensional boards with conductive paths for electrical current, in a reproducible manner and in large quantities.
The present invention has the aim of making available a process for applying electrically conductive paths on a support consisting of insulating material, which makes possible the application of conductive paths according to the particular pattern desired, in a reproducible and economic fashion, and the production of such boards in large numbers.